Fin

ABSTRACT

An improved fin assembly  100  is discussed the fin assembly  100  preferably includes a main fin body  101  and an auxiliary fin/second fin  102 . The main fin body  101  may be configured as a drop in fin, in such instances the fin body  101  includes a fin box adapter  103  which is connected to a primary fin/first fin  104  via an elongate member  105 . The auxiliary fin  102  is preferably attached to the primary fin  104  and extends substantially perpendicular to the outer face  104   1  of the primary fin  104.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to fins for use with watercraft such as surfboard, wave skis, windsurfers, water skis and the like. In particular although not exclusively the present invention is directed a composite fin with adjustable trim.

2. Discussion of the Background Art

On of the problems encountered since the beginning of surfing and similar water sports has been the stabilisation and steering of the relevant water craft in the water. Most early surfboards such as the ancient Hawaiian olo boards, and later, the hot curl boards exploited the forces of drag to stabilize them. As a result the biggest challenge in the early days of surfing was keeping the board straight and riding it in toward the beach, with the only means of control over the board being achieved by the rider by sticking a hand or foot in the water to alter the board's direction.

The advent of the fin however, radically altered the sport allowing the rider a greater degree of control over the board. The first surfboard fin appear in the mid 1930's when as surfing folk law would have it Tom Blake, nailed a scavenged boat rudder to the bottom of his board. From this humble if not crude beginning, the fin began to evolve, however it essentially remained little more than rudder until the mid-'60s, when George Greenough began applying a new type of fin to his futuristic knee machines. These fins would latter be know as high-aspect ratio fins. Greenough's inspiration for this fin type came from one of the tail fins of a blue fin tuna. This concept was then combined with aspects of aerodynamic theory, more specifically the notion that drag forces acting on the leading edge of the wing or fin are countered by the degree that they are swept back (the “aspect ratio”).

With the advent of the high aspect ratio fins the manoeuvrability of the board changed for the first time boards where provided with a type of turning leverage that allowed it to be driven and carved rather that just steered, as with the previous application of rudder-like fins. This, more than anything, laid the groundwork for the short board revolution that began in 1968 and continues to the present day.

On of the more recent developments in fin design was the introduction in 1980 by Simon Anderson of the thruster setup. The thruster is a three-fin setup wherein all the fins are the same size, with two parallel fins and a middle fin placed slightly further back on the board. The thruster provides both speed, stability during manoeuvring.

While the use of fins exploit principles of aerodynamics fin placement and setting is somewhat of an inexact science generally their placement on the board stems from trial and error research only. Modern fin arrays provide the optimum leverage and stabilizing influence when set in harmony with the board's outline and tail hips, as well as the tail rocker, vee placement and foil, or thickness taper.

One of the more recent concepts in fin design is the use of the drop in fin which enables the rider to vary fin position and fin type (i.e. thickness and taper etc). Typically most riders will select a particular fin type and setup to suit the conditions and/or their particular style. In any case the selection of the fin affects the overall ride of the board e.g. various pitches etc can cause the nose of the board to ride up or down (i.e. trim effected) depending on the conditions. This can affect both power and manoeuvrability of the board. The only way to determine if the fin setup is right for the current conditions is to get the board in the water and ride it. Once in the water it is not an easy task to change the fin setup, normally a rider would need come back into shore and alter the fin setup. In competitions this delay can be costly and a lot of the time competitors will simply look to make do with the current ride in order not to miss the opportunity for a scoring wave.

This notion of impaired ride due to fin setting not only effects surfboards but other water craft such as race skis where the difference in having the correct trim could mean the difference between winning and second. Similarly the trim of a water ski is also important when set properly the ski travels far more smoothly access the surface of the water taking stress off the skier.

Clearly there is a need for a fin arrangement that would enable riders to adjust fin setting to alter the ride of the watercraft in a relatively simple and effective manner. It would also be advantageous to provide a fin arrangement that allows for the adjustment of the ride of the watercraft when mounted in situ.

SUMMARY OF THE INVENTION Disclosure of the Invention

Accordingly in one aspect of the present invention there is provided a fin assembly the assembly including:

a body having an adaptor for attachment to a watercraft and a first fin disposed at a predetermined distance from the adaptor;

a second fin attached to the first fin wherein the second fin is movable with respect to the first fin.

The first fin is attached to the adaptor via an elongate member extending form downwardly at an angle from one end of the adaptor, the elongate member having a leading and trailing edge. Preferably the first fin extends away from the trailing edge of elongate member. In one embodiment of the present invention the fin may extend at away from the trailing edge of the elongate member at a similar angle to that formed between the adaptor and elongate member. Alternatively the first fin may extend away form the trailing edge of the elongate member at a different angle to that formed between the adaptor and elongate member. Suitably the angle between the elongate member and the adaptor is set to between 45° and 60°.

The exterior face of the first fin may include one or more contoured surfaces. The interior face of the first fin is preferably flat. The elongate member's trailing and leading edges may included one or more contoured surfaces. Suitably the adaptor is a standard fin box adaptor for a surfboard, wake board, surf ski or the like.

The second fin may be attached to the first fin such that it extends substantially perpendicular to the first fin's exterior face. Preferably the second fin is capable of movement relative to the first fin between a number of preset positions. The second fin may include projections provided on its lateral face for engagement with complementary grooves disposed on the exterior face of the first fin. Preferably the engagement of the projections with one or more of the grooves places the second fin in one of the preset positions.

Suitably the second fin is of a general aerofoil construction. Preferably the second fin includes smooth upper and lower surfaces and countered leading and trailing edges. The second fin may be generally cured with the leading and trailing edges being arcuate and extending away from the lateral face of the second fin.

The second fin may be attached to the first fin by a suitable fasting arrangement inserted through an aperture extending through the first fin and an aperture disposed in the lateral face of the second fin. The fastening arrangement may be in the form of a screw. In such instances the aperture provided in the first fin may be tapered to accept the head of the screw such that it is position substantially flush with the interior face of the first fin. The aperture provided in the second fin may be offset to the central axis of the lateral face. Suitably the aperture in the second fin is offset at an angle of 5° to the central axis of the lateral face.

BRIEF DETAILS OF THE DRAWINGS

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings, which illustrate preferred embodiments of the invention, and wherein:

FIG. 1 is a perspective view of fin assembly according to one embodiment of the present invention;

FIG. 2 is a an exploded view of the fin assembly of FIG. 1;

FIG. 3A is a side view of the main fin body of FIG. 1;

FIG. 3B is a view of the reverse side of the main fin body to that shown in FIG. 3A; and

FIG. 4 is a is a top plan view of a fin for use with the fin assembly of FIG. 1,

FIG. 5 is a perspective view of fin assembly according to one embodiment of the present invention;

FIG. 6 is a an exploded view of the fin assembly of FIG. 5;

FIG. 7 is a detailed view of camming mechanism for use with the fin assembly of FIG. 5; and

FIG. 8 is a perspective view depicting the range of movement of an element of the fin assembly of FIG. 5.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference to FIG. 1 there is illustrated a fin assembly 100 according to one embodiment of the present invention. As shown the fin assembly 100 includes a main fin body 101 and an auxiliary fin/second fin 102. In this particular example the main fin body 101 is configured as a drop in fin, and includes a fin box adapter 103 which is connected to a primary fin/first fin 104 via an elongate member 105. As can be seen in FIG. 1 the auxiliary fin 102 is attached to the primary fin 104 and extends substantially perpendicular to the outer face 104 ₁ of the primary fin 104.

As can be seen in FIG. 1 the overall sweep of the fin assembly is defined primarily by the elongate member 105 and primary fin 104. The position of the primary fin 104 at the base of the elongate member 105 also provides for further variation in fin sweep as the angle sweep between the main fin 104 and the elongate member 105 can be varied. As shown in this particular case the exterior face 104 ₁ and upper_(edge) 104 ₃ of the primary fin 104 are contoured as is the trailing edge 105 ₂ of the elongate member 105 to reduce drag.

FIG. 2 shown an exploded view of the fin assembly 100 taken from the reverse angle to that shown in FIG. 1. As shown the interior face 104 ₂ of the primary fin 104 is substantially smooth and includes a bore 107 for receipt of a fastener 108. The bore 107 in this instance has a tapered opening to receive the countersunk head 108 ₁ of the fastener 108 to ensure that the head finishes substantially flush with the interior face of the 104 ₂ of the primary fin 104. The leading edge 105 ₁ of elongate member 105 in this example is also contoured to reduce the effect of drag and turbulence produce by the elongate member 105 as it is drawn through the water. It is also apparent from FIG. 2 that the primary fin 104 has a leading edge 104 ₅ which is the same thickness as the elongate member 105.

Auxiliary fin 102 also include a bore 106 for receipt of one end of the fastener 108. As shown the bore 106 is provided in the lateral face 102 ₁ of the auxiliary fin 102. In one embodiment of the present invention the lateral face 102 ₁ may be provided with a projections 109 ₁, 109 ₂ positioned centrally on either side of the bore 106. The projections 109 ₁, 109 ₂ engage with a number of complementary grooves provided on the exterior face 104 ₁ primary fin 104 (see FIG. 3A discussed in greater detail below) to lock the auxiliary fin 102 in a number of discrete angles with respect to the primary fin 104. As can be seen from FIG. 2 the auxiliary fin 102 s of a general aerofoil construction with contoured leading 102 ₂ and trailing 102 ₃ edges.

FIG. 3A depicts the construction of the main fin body 101 in greater detail, more specifically FIG. 3A depicts the construction of the exterior face of the main fin body 101. As shown the elongate member 105 extends downwardly from the fin box adaptor 103 at a preset angle α. The angle α in this case defines the main sweep of the fin assembly 100. In this particular example the angle α at which elongate member 105 is swept back is 60°, it will of course be appreciated by those of skill in the art that the angle of sweep a could be set to any angle and will depend on the particular type of watercraft used.

The primary fin 104 in this instance in extends back form the elongate member at a substantially similar angle to that defined between the elongate member 105 and box adaptor 103. The primary fin 104 in this case includes a substantially planar region 110 for the mounting of the auxiliary fin 102. As noted above the planar region in may in one embodiment may include a series of grooves 111 _(1,1), 111 _(2,1), 111 _(3,1), 111 _(1,2), 111 _(2,2), 111 _(3,2) disposed on either side of the bore 107 for engagement with the projections 109 ₁, 109 ₂ disposed on the lateral face 102 ₁ of the auxiliary fin 102.

Depending on which pairing of grooves the projections 109 ₁, 109 ₂ are engaged with the position of the auxiliary fin 102 with respect to the primary fin will change. For example engagement of the projections with the groove paring 111 _(1,1) and 111 _(3,2) will tilt the auxiliary fin downwardly with respect to the primary fin, while engagement of the projections with the groove paring 111 _(1,2) and 111 _(3,1) will tilt the auxiliary fin upwardly with respect to the primary fin. Engagement of the projections with groove pairing 111 _(2,1) and 111 _(2,2) position the auxiliary fin substantially perpendicular to the primary fin 104 (i.e. auxiliary fin in the straight and level position). In each case altering the position of the auxiliary fin 102 alters the trim of the watercraft due to changes in force on the fin assembly 100 as it is drawn through the water.

As noted above the primary fin's exterior face 104 ₁ includes a number of contoured regions. In the present example the exterior face includes a number of contoured sections 112 ₁, 112 ₂, 112 ₃ extending between the planar region 110 and the upper 104 ₃, lower 104 ₄ and trailing 104 ₆ edges of the primary fin 104. As can be seen in FIG. 3A the lower 104 ₄ and trailing 104 ₆ edges of the primary fin have a generally arcuate profile while the upper edge 104 ₃ is relatively straight and angles downwardly from the elongate member 105 to the trailing edge 104 ₆ of the fin 104.

FIG. 3B shows the configuration of the interior face of the main fin body in greater detail. As shown the interior face 104 ₂ of the primary fin 104 is substantially flat and finishes flush with the contoured edges of the elongate member 105. The bore 107 in this instance is positioned adjacent the leading edge 104 ₅ of the primary fin 104 and at approximately the centre of balance of the main fin body 101.

While the above discussion of the main fin body 101 focuses on a particular construction for the primary fin 104, it will of course be appreciated by those of skill in the art that other fin shapes, thickness and sizes can be utilised with the present invention. For instance fins having different sweeps and pitches to the contoured sections could be utilised.

FIG. 4 depicts the construction of the auxiliary fin 102 according to one embodiment of the present invention in greater detail. As shown the auxiliary fin has a generally acuate shape with the leading 102 ₂ and trailing 102 ₃ curving outwardly and backwardly from the lateral face 102 ₁. The upper 113 and lower 114 (not shown) surface of the auxiliary fin are substantially flat with three interfaces between the leading and trailing edges and the upper and lower surface of the fin being contoured. The bore 106 in this particular example is positioned at an angle β to the central axis 115 of the lateral face 102 ₁ of the auxiliary fin.

FIG. 5 depicts an alternate construction of a fin assembly 200 according to the present invention. As shown the fin assembly includes a primary fin 201 and an auxiliary fin/second fin 202. As in the case of the above example the primary fin 201 is configured as a drop in fin, and includes a fin box adapters 203. Unlike the fin assembly shown in FIG. 1 the primary fin 201 is a unitary body more specifically the primary foil 204 and leg 205 are formed integrally. The secondary fin 202 is attached to the foil 204 and extends substantially perpendicular to the outer face 204 ₁ of the foil 204.

An exploded view of the fin assembly 200 of FIG. 5 is shown in FIG. 6. In this particular example the secondary fin 202 is attached via a camming mechanism 206. The camming mechanism 206 in this case includes a series of teeth 207 for complementary engagement with a series of teeth 208 provided about the circumference of bore 209 provided in the outer face 204 ₁. The secondary fin 202 in this instances is attached to the foil 204 of the primary fin 201 via a fastener 210 inserted from the rear face 204 ₂ of the foil through aperture 211. As above the fastener 210 is positioned such that its head finishes flush with the interior face of the 204 ₂ of the foil 204.

A more detailed view of the camming mechanism 206 of the auxiliary fin 202 is shown in FIG. 7. As shown the camming mechanism includes a series of teeth 207 disposed about its circumference. The teeth 207 in this case are shaped for complementary engagement with teeth 208 disposed circumference of bore 209 provided in the outer face 204 ₁. Each tooth within the series of teeth 207 is tapered, while each tooth in the series of teeth 208 includes a complementary taper such that when the camming mechanism 206 is positioned within the bore 209 the teeth in each series 207, 208 mesh. The meshing of the teeth and the pressure applied acts to hold the secondary fin 202 in a predetermined position with respect to the primary fin. In addition it is possible to rotate the secondary fin 202 up or down by applying sufficient via the pressure on the camming mechanism 206 to cause rotation of the teeth within the series of teeth 207 over the teeth in series of teeth 208. That is the teeth series of teeth 208 effectively act as pawls for ratcheting the camming mechanism 206 to the next position through the series of teeth 207.

The range of motion of the secondary fin 202 with respect to the primary fin 201 is shown in FIG. 8. As can be seen in this example the secondary fin 202 can be positioned in at a number of discreet angles from the horizontal position 212 ₁. The angular variation in this instance is defined by the interaction of the series of teeth 207 with the series of teeth 208. By rotating the secondary fin 202 and subsequently the camming mechanism 206 either clockwise or counter clock wise changes the angle of declination or inclination of the fin. As noted about rotation of the teeth within the series of teeth 207 over the teeth in series of teeth 208 effectively ratchets the fin to the next position. More specifically each tooth within the series of teeth 207 moves forward or backward into engagement with the next tooth within series of teeth 208. In each instance the movement of the teeth to the next position varies the angular position of the fin a few degrees e.g. between 2° and 5°.

As shown in FIG. 8 the secondary fin 202 can be tilted 212 ₂ up respect to the primary fin, by rotating the camming mechanism 206 counter clockwise. Rotating the camming mechanism 206 clockwise cause the fin 202 to be angled downwardly 212 ₃ with respect to the primary fin 201. At each stage of moment of the camming mechanism 206 the teeth interact to hold the secondary fin at the desired angle. To limit further movement the fastener 210 may be tightened. In such instances the fastener may include a quick release mechanism to enable the fastener 210 to be tighten and loosen by the user of the watercraft to change and lock the auxiliary fin at a desired angle. In each case altering the position of the auxiliary fin 202 alters the trim of the watercraft due to changes in force on the fin assembly 200 as it is drawn through the water.

It is to be understood that the above embodiments have been provided only by way of exemplification of this invention, and that further modifications and improvements thereto, as would be apparent to persons skilled in the relevant art, are deemed to fall within the broad scope and ambit of the present invention described herein. 

1. A fin assembly the assembly including: a body having an adaptor for attachment to a watercraft and a first fin disposed at a predetermined distance from the adaptor; a second fin attached to the first fin wherein the second fin is movable with respect to the first fin.
 2. The fin assembly of claim 1, wherein the first fin is attached to the adaptor via an elongate member the elongate member having a leading and trailing edge.
 3. The fin assembly of claim 2, wherein the first fin extends away from the trailing edge of elongate member.
 4. The fin assembly of claim 3, wherein the elongate member extends downwardly from one end of the adaptor at an angle between 45° and 60°.
 5. The fin assembly of claim 3, wherein the elongate member extends downwardly from one end of the adaptor at an angle of 60°.
 6. The fin assembly of claim 4, wherein the first fin extends from the trailing edge of the elongate member at the same angle formed between the adaptor and elongate member.
 7. The fin assembly of claim 4, wherein the first fin extends from the trailing edge of the elongate member at a different angle to that formed between the adaptor and elongate member.
 8. The fin assembly of claim 2, wherein the elongate member's trailing and leading edges included one or more contoured surfaces
 9. The fin assembly of claim 1, wherein the first fin's exterior face includes one or more contoured surfaces.
 10. The fin assembly of claim 1, wherein the first fin's interior face is substantially flat.
 11. The fin assembly of claim 1, wherein the second fin extends substantially perpendicular to the first fin's exterior face.
 12. The fin assembly of claim 1, wherein the second fin is capable of movement relative to the first fin between a number of preset positions.
 13. The fin assembly of claim 12 wherein the second fin include projections provided on its lateral face for engagement with complementary grooves disposed on the exterior face of the first fin.
 14. The fin assembly of claim 13 wherein engagement of the projections with one or more of the grooves places the second fin in a preset position.
 15. The fin of claim 1, wherein the second fin includes smooth upper and lower surfaces and countered leading and trailing edges.
 16. The fin assembly of claim 15, wherein the leading and trailing edges are arcuate and curve away from the second fin's lateral face.
 17. The fin assembly of 12, wherein the second fin is attached to the first fin by the insertion of a fastener through apertures provided in the first and second fin.
 18. The fin assembly of claim 17 wherein the aperture provided in the first fin is tapered such that the head of the fastening device is position substantially flush with the interior face of the first fin.
 19. The fin assembly of claim 17 wherein the aperture provided in the second fin is offset to the second fin's lateral face's central axis.
 20. The fin assembly of claim 19 wherein the aperture in the second fin is offset at an angle of 5° to the central axis of the lateral face.
 21. The fin assembly of claim 1, wherein the adaptor is a fin box adaptor for a water craft selected from at least one of the following surfboard, wake board, paddle broad, kayak or surf ski.
 22. The fin assembly of claim 12, wherein the second fin is positioned between the present positions via the use of a camming mechanism.
 23. The fin assembly of claim 22, wherein the camming mechanism includes a first series of teeth disposed about its circumference for complementary engagement with a second series of teeth disposed on the first fin.
 24. The fin assembly of claim 23, wherein the rotation of the camming mechanism causes the each tooth within the first series of teeth into engagement with the next available tooth within second series of teeth. 